Dental impression composition



Patented Oct. 13, 1936 OFFICE DENTAL IMPRESSION COIWPOSITION Raymond B. Stringfield, Signor to Dental Plasti les, Calif., a corporation of California Los Angeles, Calif., ascs Company, Los Ange- No Drawing. Application July 18, 1933,

. SerialNo. 681,004

9 Claims. (CI. 18-47) This invention relates to a dental composition and morespecifically it relates to a composition of matter to be employed in the preparation of dental impressions.

For many dental purposes such as the making of full dentures, partial dentures, bridges, etc. it is necessary for the dentist to be able to accurately reproduce portions of the mouth of the subject. Such reproductions often involve the duplication of undercuts ofmore or less severity, as for instance in the case where a tooth or teeth have been extracted and the adjacent teeth have crowded together.

For many years dental impressions have been taken with materials such as plaster of Paris,

or various shellac or wax compositions. These materials have little or, no elasticity and while it is not. difficult to take some impressions with them, such as for most full dentures, 'itis not possible to reproduce accurately undercuts with out either breaking the impression and re-assembling it as is done with plaster, or. taking the im-- pression in sections as is;the practice'in the use of shellac and waxcompounds. The-foregoing methods obviously involve time and-there is the danger of. inaccuracy, as well as discomfort to the patient. 7 w By the use of an. impression material which may be introducedin the mouth in a fluid or-plastic condition and cooledto an elastic state, it is possible to take an impression which will accu-i rately reproduce all details of the portion of the mouth undenexamination and which-due to itselasticity, can be removed from any undercuts present without losing the accuracy of the im,-. pression. i

Due to'the narrow range of temperaturewhich the human mouth can stand, rather strict limitations are placed on the types of elastic materials which canbe'iu'sed. These materials must obvi ously be either fluid orpla-stic when they are seated to place in the mouth and must change by cooling to an elastic gel which will permit removal from the undercuts without permanentdistortion. They must also either hardento a solid or. be a sufiiciently" tough and rigid gel so th t they may be used as molds for models of plaster or other compounds to be poured intothem. 'i It is possible by the use of. a hydro-colloid to obtaida'compound which is a viscous fluid when slightly warmed and whichcools at, room temperature, or by-the use of ice water, to a, gel which is elastic enough to, reproduce undercuts properly andis also suiiiciently firm to withstand a reasonable ,arnount ofhandling and whichcan be used as a mold to receive plaster. The hydro-colloid types of denture materials are objectionable because they require special equipment to insure the correct proportion of water in the mixture, and proper cooling of the impression in the mouth in order to obtain the necessary degree of rigidity or toughness. Furthermore, impressions made from hydro-colloids are relatively fragile and are easily injured when handled. Additionally it is necessary to supply some means for the preven- 4 tion of the evaporation of w ter from the impression after it has been removed from the mouth, otherwise a change of shape or size in the impression takes place.

The use of non-aqueous gels in the production of dental impressions eliminates most of the objections inherent in other types of impression materials. These non-aqueous gels may be made in various ways. However, I find the most suitable types to be made by the action of metallic soaps, such as aluminum stearate or palmitate, with waxes or pitches such as stearine pitch. Gels produced in this manner become plastic when warmed instead of liquid as dothe aqueous gels and may be so compounded that they form an elastic mass at temperatures slightly above the temperature'of the mouth (98.6" F.). Thus no special cooling is required in order to obtain the proper degree 'of rigidity in the impression material. When impressions made using thjesegels are removed from the mouth and further cooled; they become quite rigid and may be handled without any unusual or special precautions to prevent a change in shape or size.

An ideal dental impression material should have the following characteristics:

' 1. It must accurately reproduce all details of the impression. J y my 2. It must changefrom a plastic to an ela's'ti'c gel at a temperature comfortable to the mouth.

3. It must be workable in the fingers without sticking so that the dentist may properly load a tray. 4. It must not stick to the teeth or gums when the impression is being removed. In some cases the removalof the.impression is,assisted by the use of a separating medium, such as glycerine or a glycerine jelly which is applied to the teeth prior to taking the impression.

5. It must not have, an obnoxious taste or odor, or be injurious to the mouth tissue.

6. It' must not decompose appreciably when placed in water to cool.

i {7. The impression must not change dimengel with the sions upon standing for several hours at cool room temperatures.

8. The impression should be removable from the plaster model without sticking, although it is feasible at times to aid this property by the use of a thin separating medium, such as alcoholic solutions of sandarac, or other resins, applied to the impression before pouring the plaster.

Most gels produced from waxes and metallic soaps are not tough and are difficult to handle due to their fragility and also because they stick to the plaster cast. I have discovered-that these gels may be improved by the substitution of a tougher material for a part, or all, of the waxes. By the substitution or all of the wax, it is possible to obtain a gel with metallic soaps which has greatly improved physical characteristics when employed in the production of dental impression compositions. Stearine pitch is a by-product of the stearic acid industry. It is a complex mixture of stearine, stearine acid and other materials. It is black in color due to the carbon formed by decomposition. during manufacture. When cooked with a metallic soap, as for example, aluminium stearate or palmitate, at a temperature of approximately 400 F. it produces a composition which upon cooling forms a gel.

In some instances the stearine pitch is quite acid and it is necessary to partially neutralize this pitch in order to obtain a satisfactory gel during preparation with most metallic soaps. However, I have discovered that acidity is of little importance in the production of gels from stearine pitch with aluminium palmitate. Stearine pitch which is too acidic to produce gels with aluminium stearate, readily gels with aluminium palmitate.

These gels are extremely tough and elastic and possess considerable elasticity even when cooled to a low temperature. The softening point of this gel may be varied over an appreciably wide range by varying the quantity of metallic soap used.

- Other materials, such as asphalt or coal tar, may be substituted for part or all of the stearine pitch Furthermore I may also employ pitches formed during the manufacture of oleic, palmitic, lauric, or other fatty acids, and when I employ the term pitch in the specification and claims, it will be understood to embrace any or all of the foregoing materials. Furthermore, while aluminum palmitate is found to be a very satisfactory metallic soap for the preparation of the stearine pitch, I find that other metallic soaps are capable of producing satisfactory gels with; stearine pitch. For example, I ay a so employ iron stearate, ironpalmitate, iron .laurate, aluminum stearate, aluminum laurate or aluminum naphthenate in the place of aluminum palmitate for the production of the gel with stearine pitch, coal tar, asphalt, or other pitches described above. Moreover, a metallic soap of zinc, calcium, magnesium or other metal may be substituted for all or part of the aluminum palmitate.

The gels produced by the combination of pitches with the foregoing metallic soaps may be compounded with various materials, such as waxes, wax gels, synthetic waxes, mineral fillers such as talc or clay, natural or synthetic resins, organic fillers such as starch, perfumes, water, glycerines, glycols, graphite, or lubricants for the production of a large number of plastic compositions suitable for use in the dental art of stearine pitch for a part,

and elsewhere where impressions, casts or models are employed. For example, compositions may be formulated suitable for the reproduction of facial or other anatomical features, or for the duplication of models, etc.

It is, therefore, an object of my invention to produce gels from metallic soaps and pitches.

It is a further object of my invention to produce gels by combining stearine pitch with a metallic soap, such as aluminium palmitate.

It is a further object of my invention to produce impression compositions by compounding gels produced from pitches and metallic soaps with fillers, waxes, resins, water, polyhydric alcohols, graphite or oils. or mixtures thereof.

It is a further object of my invention to produce impression compositions by compounding gels produced from stearine pitch and aluminium palmitate with fillers, waxes, resins, water polyhydric alcohols, graphite or oils or mixtures thereof. 7

It is a further object of my invention to produce impression compositions so compounded that they become elastic gels at or slightly above 98.6 F., and thus require no special cooling in order to obtain the proper degree of rigidity when used for dental impression purposes.

These gels and especially the gel produced from stearine pitch and metallic soaps are highly satisfactory as bases to be compounded with other materials as I have previously described.

In the preparation of the gel from stearine pitch and aluminium palmitate I proceed as follows:

15 pounds of stearine pitch are melted in a kettle over an open flame and the temperature raised to approximately 350 F. 7 pounds of aluminum palmitate are then added and the mixture agitated while the temperature is raised to approximately 400 F., andheating and agitation continued until a smooth viscous mass is obtained which on cooling sets to a firm gel.

The firmness and softening point of this gel may be modified by usingmore or less of the metallic soap, or by the addition of plasticizers such as fatty acids, rosin, abietic acid, waxes, etc. It is also possible to add resins or waxes of high melting point, such as synthetic wax to increase the firmness of the gel when cooled.

An example of a composition which I have found to be highly satisfactory for making dental impressions and which contains stearine pitch gelled with a metallic soap is as follows:

Pounds Stearine pitch, M. P. 150 F 90 Stearic acid 13 Latex 15 Aluminum palmitate 35 Gel of 60 parts Japan wax and 40 parts aluminum palmitate 30 Talc, 200 mesh or finer 36 Water 15 increased to approximately 400 The mixture is then allowed to cool to approximately 200 F. and the Japan wax gel, which has been previously prepared by heating parts of Japan wax with 40 parts of aluminum palmitate at approximately 350 F. until homogeneous and cooling, is added, together with the talc and water, and the whole thoroughly mixed.

The addition of the and increases its specific gravity so that it can be made floating or non-floating as desired. The proportion of aluminium palmitate may be varied to some extent with difierent lots of stearine pitch. Too small an amount produces a gel which is too soft and somewhat sired for any particular purpose, and also to add stiffening agents, such as synthetic Wax having a melting point above 100 C. to render the material harder when cold and more easily removed from plaster cast into an impression taken with this composition.

A further example of a composition which I have found to be highly satisfactory for making dental impressions and which contains stearine pitch gelled with a metallic soap is as follows:

. Pounds Stearine pitch (melting point) 150 F Synthetic wax having a melting point above C 19 Aluminium palmitate 40 Rosin 7 Talc 10 Water 5 In making this composition, the stearine pitch and are melted together, the aluminium palmitate added, and the temperature F. and agitation maintained until a smooth mixture is obtained which on cooling becomes a stiff gel. The mixture is then allowed to cool to appoximately 200 F. and the rosin added, and when this has dissolved and the mixture been agitated until smooth, the tale and water are added and the whole thoroughly mixed.

In this composition, the synthetic wax softens the mixture when warm and renders it harder when cold, while the rosin plasticizes the stearine pitch-metallic soap gel and aids the emulsification of the water which also plasticizes the composition. The talc adds smoothness and weight.

The above compositions are adapted to become plastic within a temperature range comfortable the impression tray or other appliance to be used. He then loads the tray or appliance suitably with the plastic material, seats it to place in the mouth,

1. An impression material comprising a fatty acid pitch jelled with a metallic soap.

2. An impression material comprising a fatty acid pitch jelled with a metallic soap of palmitic acid.

3. An impression material comprising stearine pitch gelled with a metallic soap.

4. An impression material comprising stearine pitch gelled with a metallic soap of palmitic acid.

5. An impression material comprising stearine pitch gelled with aluminium palmitate.

6. An impression material comprising stearine pitch, synthetic wax having a melting point above 100 C., aluminium palmitate, a mineral filler and water.

7. An impression material comprising approximately 90 thetic wax having a melting point above 100 C.,

mineral filler, and 1 part of water.

8. An impression material comprising stearine pitch, synthetic wax having a melting point above 100 C., aluminium palmitate, rosin, a mineral filler and water.

9. An impression material comprising 90 parts of stearine pitch, 19 parts of synthetic wax having a melting point above 100 C., 40 parts of aluminium palmitate, '7 parts of rosin, 10 parts of talc and 5 parts of water.

RAYMOND B. STRINGFIELD.

palmitate, 10 parts of a l 

